The present invention relates to a copier, facsimile transceiver, printer or similar image forming apparatus having a device capable of identifying an image orientation to allow adequate processing to be executed and a device for binding sheets carrying images thereon by determining a binding position.
A document image processing apparatus has been proposed in various forms in the past. Japanese Patent Laid-Open Publication No. 250184/1989, for example, discloses a document image processing apparatus which separates a character image from image data representative of a document and read by a scanner, extracts a characteristic amount of the character image, converts the characteristic amount in matching relation to the rotation angle of the character, compares the converted characteristic amount with a dictionary to thereby recognize the rotated image or, when the rotation angle of the character is not known beforehand, recognizes the separated character image as two or more rotated images of different angles and thereby determines the rotation angle of the character.
On the other hand, Japanese Patent Laid-Open Publication No. 105266/1989 teaches a document image processing apparatus which separates a suitable number of character images in the vertical direction from the image data of a document read by an image scanner (separates such that the width from the head portion toward the tail portion of a line and the width from the tail portion toward the head portion are equal to each other). Paying attention to the fact that a greater number of black pixels exist in the width from the head portion to the tail portion than in the width from the tail portion to the head portion, the apparatus determines the position of the image in the top-and-bottom direction and, if it is upside down, rotates it by image rotating means to a correct position.
Although the above-described conventional apparatuses identify a character orientation (document image orientation) by using a character recognition scheme, they lack a measure for coping with the occurrence that an image orientation cannot be identified on the basis of an object which is the reference for identification.
The identification of a character orientation has not been much applied to an image forming art, particularly a binding technology, although it would facilitate convenient image formation. Regarding image formation accompanied by a binding operation, the orientation of a document relative to an image reading section is an important consideration since it is apt to cause sheets to be bound at an inadequate position. Since an ordinary binding device binds sheets at only a particular position relative to the document set position for mechanical reasons, an erroneous orientation of documents disturbs the binding position. Specifically, if sheets can be bound at any desired position thereof, they will be bound at an adequate position when at least the orientation of the documents is accurately detected. However, an ordinary binding device has a stapler which is fixed in place or movable only along one end of sheets due to the mechanical limitations of the device body. It is, therefore, necessary to match the orientation of the documents to the reference binding position of the binding device. For example, should vertically long horizontally written documents be set upside down in the top-and-bottom direction and should the binding device be expected to bind the upper left corner of documents, sheets would be bound at the lower right corner.
Moreover, it often occurs that when a great number of document images are handled in a stack, image data exist in the binding range of some document images, causing sheets to be bound in image areas thereof. In addition, in the event of punching or sorting, the mixture of sheets of different orientations are also obstructive.